Cathodo-luminescent display panel

ABSTRACT

This disclosure depicts cathodo-luminescent devices and luminescent panels employing X-Y matrices of such devices as the display elements. The cathodo-luminescent devices are depicted as each comprising a two-section cell containing an ionizable gas at very low pressure. The first section comprises an electronmultiplier serving as a controllable source of free electrons. Free electrons are drawn from the electron-multiplier and accelerated in the second section to high energies whereupon they collide with a light-emissive phosphor screen. Other structures including means for modulating the flow of electrons to the screen are disclosed.

United States Patent 1 Schwartz 51 Sept. 9, 1975 1 CATHODO-LUMINESCENT DISPLAY PANEL [75] Inventor: James W. Schwartz, Glenview. 111.

[73] Assignee: Zenith Radio Corporation, Chicago Ill.

[22] Filed: Jan. 14, 1974 [21] App]. No.: 433,186

[56] References Cited UNITED STATES PATENTS 3374.380 3/1968 Goodrich 1 313/105 X 3,505,559 4/1970 Jeffries et a1. 315/12 ELECTRON MULTIPLIER 38 $772,551 11/1973 Grant 313/105 X Primary ExaminerJames W. Lawrence Assistant Examiner--E. R. LaRoche Attorney, Agent, or Firm-John H Coult [57] ABSTRACT This disclosure depicts cathodo-luminescent devices and luminescent panels employing X-Y matrices of such devices as the display elements. The cathodoluminescent devices are depicted as each comprising a two-section cell containing an ionizable gas at very low pressure. The first section comprises an electronmultiplier serving as a controllable source of free electrons. Free electrons are drawn from the electronmultiplier and accelerated in the second section to high energies whereupon they collide with a lightemissive phosphor screen. Other structures including means for modulating the flow of electrons to the screen are disclosed.

11 Claims, 8 Drawing Figures ION GENERATION STAGE 62 48L 521 f 6 CATHODE is ION 54 ELECZTRONS 50 54 l 56 gal] PHOSPHOR SCREEN 58 PATENTED 9 i975 sum 1 OF 5 mm Zmwmow mOImwOIm wn 3 S 595 52 20536 N0 wwanrm ZOEEwZwQ 29 PATENIEB SE? 9 i975 saw 2 of 5 PAI'ENIEUSEP 9x975 sum 3 OF 5 6 N 2 8 w T q l W D OS O NN E RLAR wC E D v0 S R P 0 0 2% 5 A Y LIIR IIIO M mmmm OH c w W W U O L T OIIS HH mm L PATENTED 9 I975 SIIIET 0F 5 MQN VMT

CATHODO-LUMINESCENT DISPLAY PANEL CROSS-REFERENCE TO RELATED APPLICATION This application relates to. but is in no way dependent upon. copending application Ser. No. 538.486, filed Jan. 3, I975. assigned to the assignee of the pres ent invention.

BACKGROUND OF THE INVENTION The evolution of television and other displays has been toward structures which are capable of reproducing ever larger and brighter images. yet which are ever less bulky and lighter. Because of seemingly inherent limitations of cathode ray tubes which prevent attainment of compact large'screen television receivers. other approaches, many of them radically different from cathode ray tubes. have been investigated.

It has been recognized that other avenues of investigation. to be viable, must potentially lead to display structures capable of reproducing images having adequate brightness and luminous efficiency and preferably having acceptable color rendition. A popular and widely investigated approach has utilized light-emissive elements arranged in X-Y matrices, selectively encrgized by means of row and column selectors and drivers. Light-emitting diodes. gas discharge devices and liquid crystal devices have been explored as possible display elements for use in such matrix-type devices. The utilization of display elements arranged in an XY matrix for row column selection has imposed its own set of requirements, including the requirement that the individual picture elements be capable of individual control without partial encrgization of unselected elements.

PRIOR ART 2.868.994 Anderson 3.243642 Gehel 3.262,!) I ll Kalan 3.27 l ,66l (ioodrich et al 3.483322 Novotny 3.492.523 Smith et al 3.5 l=l 87ll Jensen 3.600627 Goede et al 1622,82) Watanahc 3.646.382 Goedc ct al 3.693.004 Sanford 3.725.731 Kamn 3.771.008 Chen et al OBJECTS OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however. by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. I is a highly schematic view of a gas discharge diode of a type well known in the art;

FIG. 2 illustrates in highly schematic form a low pressure gas cell containing an electron-multiplier;

FIG. 3 is a highly schematic view of a cathodeluminescent device constructed in accordance with the principles of this invention;

FIG. 4 is a fragmentary perspective view of a device similar to the FIG. 3 device, shown in a more structural. less schematic representation;

FIG. 5 shows in highly schematic form a television display panel utilizing cathodo-luminescent devices constructed to implement the teachings of this invention'.

FIG. 6 is a schematic fragmentary perspective view, broken away. of a display panel representing a preferred mode of execution of the invention;

FIG. 7 is a sectioned elevational view of the panel shown in FIG. 6, taken along lines 7-7 in FIG. 6; and

FIG. 8 is an enlarged fragmentary sectional view taken along lines 8-8 in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principles of this invention are preferably implemented in apparatus which employs a low pressure gas cell containing an electron-multiplier which serves as an efficient source of free electrons and which has a threshold switching capability to enable mutually exclusive selection of elements in an X-Y matrix of elements. The free electrons generated in the electronmultiplier are accelerated in an accelerating stage into impingement with a cathodo-luminescent phosphor screen. Before discussing the details of a display panel constructed according to this invention. there will be discussed certain basic principles underlying and employed in cathodo-luminescent devices according to this invention.

In a simple gas diode (see FIG. 1), positive gas ions generated in the gas impinge upon the cathode. releasing secondary electrons. The electrons are accelerated toward the anode. The probability of interaction with a gas atom in the intervening space depends upon the density (pressure) of gas molecules in that space and the length of the path. When an electron has gained sufficient energy in falling through the electric field along the cathode-toanode path, it can ionize a gas atom. thus freeing an additional electron and creating a feedback ion. The two electrons (the original one plus the newly formed one) proceed toward the anode, perhaps creating additional ion/electron pairs on the way. Some ions and electrons will be lost to the walls. In general, each backwardly accelerated ion impinging upon the cathode will free an average of less than one electron perhaps as few as l electron per l0 ions impinging. Hence. for a sustained discharge, each electron leaving the cathode must initiate an avalanche of ion/electron pair generating collisions such that enough ions are generated on the average to satisfy wall losses and to generate collectively one new secondary electrode at the cathode.

Obviously. if the density of gas is not sufficient to allow an adequate number of collisions along the cathode to-anode path, a discharge cannot be maintained. Increasing the path length increases the probability of a collision at a given pressure. Raising the voltage difference helps in a marginal situation, primarily because the electrons will be accelerated to the minimum ionizing level sooner along the path (thus increasing the effective path length). and because occasionally more than one electron may be released per collision. On the other hand. high velocity electrons may have reduced ionization probability. The net result is that if a path is too short. for a given gas density. a self-sustained discharge cannot be maintained even when very high voltage differences exist in the field-containing space. This circumstance is classically described by a Paschen curve. This curve and other principles and details of gas discharge devices and their operation are described in such works as Gaseous Conductors. by James Cobinc. Dover Publications (1958).

The term gas discharge cell" or gas discharge dcvice"- is herein intended to mean a cell or a device in which the electric fields differ significantly between the on" state wherein a plasma is present and the off state wherein no current is flowing. Devices constructed in accordance with this invention do not have the described characteristics of a gas discharge device. Rather. they may be aptly termed electrostatic devices in which the electric fields established within by application of voltages to its electrodes are not substantially and abruptly altered by the presence of ions.

In a conventional gas discharge diode as shown in FIG. I. the design relationship between gas pressure *p" and the cathode-to-anodc spacing 71". for minimum operating voltage. is given to excellent approximation by the Paschen similitude expression: p X d= K. where K is a constant which depends on cathode material, gas composition and tube geometry (but not tube size). For usual discharge devices. K is generally equal to about one-half torr cm.

In the FIG. I diode. electrons emitted from the cathode undergo ionizing collisions in the gas. resulting in an electron avalanche" which multiplies the electron current as it approaches the anode. If the ion-electron secondary emission ratio is I/.\' (typically about 0.1). a gas-electron-avalanchc gain of at least (where .r is typically about l) must be developed to establish an electron-ion loop gain of unity. Accordingly. the minimum breakdown voltage characteristic for a given diode (revealed) by the well-known Paschen curve) is a measure of the secondary emission properties of the cathode of the diode. as well as a measure of the electron-avalanche properties of the gas.

As will be explained in more detail hereinafter, in accordance with the principles of this invention. an electron-multiplier. as shown schematically in FIG. 2, is in serted between the cathode and the region where ions are to be generated. The illustrated FIG. 2 device comprises an envelope I0 containing an ionizable gas such as hydrogen, helium. neon or other suitable gases or gas mixtures. A cathode I2 serves as an electron emitter. A plurality of serially arranged. secondary-electronemissive dynodes I4, l6, I8, 20, 22 and 24 receive applied voltages ever-increasing in positive polarity in a direction away from the cathode 12. The voltages are shown as being provided by a tapped voltage divider 26. A final anode 28 collects the electrons from the last dynode 24.

Due to collisions between the electrons and the gas atoms within the envelope 10, positive gas ions 30 are generated. In accordance with this invention, as will be explained in more detail hereinafter, the dynodes 14-24 are arranged so as to permit the ions 30 to be accelerated directly to the cathode 12 to cause the cathode to emit additional free electrons 32.

For the FIG. 2 device, the Paschen similitude expression takes the general form:

p'l'g K. where I is the effective length of the ion generation region and g' is the gain of the electron-multiplier. The value of K depends upon the efficiency with which positive ions are transported back to the cathode and the ion-induced secondary electron emission coefficient of the cathode. This is true whether or not an electron-multiplier is included. K also depends upon the electron velocity in the ion generation region. In appropriately designed tubes, however, the value of K is not likely to differ greatly in general magnitude whether a multiplier is present or not. Hence it may be concluded that if an electron-multiplier of gain g is interposed, a discharge may be initiated at a pressure which is approximately l/g lower than if a multiplier is not interposed. This principle is basic to this invention.

By operating a tube at sufficiently low gas pressure. ionizing collisions between gas atoms and electrons becomes a negligible effect so far as scattering of electrons is concerned. Under such conditions a beam of electrons may be accelerated to high velocity with no significant energy loss and no concern about initiating an unwanted self-sustained discharge between the high voltage anode and lower voltage electrodes in the tube.

FIG. 3 illustrates in highly schematic form a cathodeluminescent device containing basic components of devices constructed according to this invention. The FIG. 3 device 34 is illustrated as comprising wall means in the form of an envelope 36 (typically glass) which defines an enclosure containing an ionizable gas such as helium, hydrogen, neon or other suitable gases or gas mixtures at a predetermined pressure sufficiently low to preclude establishment of a gas discharge in the device.

An electron-multiplier 38 located within the enclosure creates at an output end thereof a source of electrons. The electron-multiplier 38 includes a cathode 40, which may comprise, for example. an aluminum, magnesium or nickel strip. The electron-multiplier 38 is depicted as including a plurality of discrete dynodes 42, 44, 46, 48, 50 and 52. The dynodes 42-52 may be composed, for example, of oxidized beryllium-copper alloy, cesium-antimony alloy, silver-magnesium alloy. oxidized aluminum, or other suitable materials. The last dynode in the FIG. 3 embodiment 52) and in laterdescribed embodiments is also referred to herein as the electron-multiplier anode. As used. this term is intended to mean the highest voltage dynode in an electron-multiplier constituting a pair of a light-emissive device constructed according to this invention, and is not intended to mean a current-collecting electrode.

As in the FIG. 2 device, the dynodes are adapted to receive voltages ever-increasing in positive polarity in a direction away from the cathode 40, which pattern of voltages may be provided by a voltage divider. as shown at 26 in FIG. 2. This invention comprehends the use of an electron-multiplier of a type other than as shown, such as a channel plate multiplier. a Weis mesh multiplier, or a staggered plate multiplier; the illustrated shaped dynode structure is preferred however.

The electron-multiplier 38. of whatever form. gener ates positive gas ions 54 as a result of collisions between the electrons and gas atoms within the multiplier. In accordance with this invention. as will be explained in more detail hereinafter. the dynodcs 42-52 are arranged so as to permit the positive gas ions 54 to be accelerated to the cathode 40 to cause the cathode to emit additional free electrons 56. The additional electrons 56 emitted from the cathode 40 as a result of the ion bombardment are in turn multiplied in the elec tronmultiplier 38. The electron-multiplier 38 thus constitutes part of a regenerative electron-ion feedback loop.

Phosphor means in the form of a phosphor screen 58 is disposed at one end of the enclosure in spaced relation to the output end of the electron-multiplier 38 for emitting light when bombarded by high energy electrons. As will become evident as this description proceeds. the phosphor material may be selected to emit white light for use in a one-color display device or panel. or may be. for example. red-emissive. blueemissive and green-emissive in arrays of devices designed to form color television pictures or other color displays. It should be noted that only a small percentage of the multiplied electron beam is utilized to create positive gas ions. at very substantial part of the beam being available for acceleration to the phosphor screen 58.

An accelerating anode 60 is disposed at the phosphor screen 58 and is adapted to receive a predetermined accelerating voltage which is substantially higher than the voltage impressed on the last dynode 52 (the electron-multiplier anode) of the electron-multiplier 38. The accelerating anode 60 draws electrons from the electron-multiplier when the electron-multiplier is in an active state and accelerates the electrons to high en ergies for impingement upon the phosphor screen 58.

In the illustrated form of the invention. an ion generation region or stage 62 is provided between the last dynode 52 and the accelerating anode 60 to provide a maximized electron-gas interaction probability. Additional field-forming electrodes may be provided in such a special ion-generating region to optimize the field characteristics for maximum ion generation. As described hereinafter with respect to another embodiment of the invention. ion generation may. alternatively. be accomplished within the compass of the dy nodes 4252, thus obviating a separate ion generation region within the device. The provision of a separate ion generation region improves the efficiency of ion generation and ion feedback efficiency. but adds to the length of the cathode-luminescent device and thus increases the front-to-back depth of a display panel made up of such devices.

In accordance with this invention. activating means are provided for selectively causing the loop gain of the electronmultiplier feedback loop to be less than unity when it is desired to cause the electron-multiplier to assume an inactive state. or for turning the electronmultiplier on by causing the said loop gain to be unity or greater. In the illustrated preferred embodiment. the electron-multiplier is self-saturating due to space charge and other effects. Thus when the electronmultiplier is turned on, it is done so by causing the loop gain to momentarily exceed unity wherein the electronmultiplier saturates at a predetermined saturation current level and the gain becomes exactly unity. It is coir lll templated that devices may be built. however. which follow the teachings of this invention but which are not driven to saturation in the on state.

By way of background. the loop gain" is taken to be the average number of electrons ultimately released from the cathode in a complete cycle by the action of a single electron starting from the cathode. The loop gain is thus equal to the product of the following:

I. the gain of the electron-multiplier 38,

2. the gas ionization probability due to a single output electron.

3. the probability that an ion generated in the ion generation region will fall back to the cathode. and

4. the secondary-clectron-emission coefficient of the cathode upon ion bombardment.

If the loop gain exceeds unity. the current in the loop builds up exponentially until some saturation effect such as space charge alters the electrical lields within the electron-multiplier and reduces the gain to unity. The loop current then stabilizes at that level. If the loop gain is caused to fall below unity. the current exponentially falls towards zero.

Thus in the context of the preferred FIG. 3 selfsaturating device. the device may be bi-stably driven between an off state and an activated on state by selectively causing the loop gain to be either less than unity or. alternatively. unity or greater than unity. In FIG. 3. the device activating means is illustrated as a switching means for applying to the cathode 40 a positive voltage of such a value that the electron-multiplier gain drops below that level necessary to establish a loop gain of unity or greater. To turn the device on. a cathode volt age is selected which. in combination with the voltages applied to the dynodcs 42S2. establishes a gain in the multiplier 38 which is adequate to cause the loop gain of the device to be unity or greater.

It is manifest that by the expedient of a bi-stable switching mechanism which switches the loop gain between less than unity and unity or greater. the electronmultiplier 38 can be switched between off and on states in a highly non-linear fashion.

It is contemplated that cathode-luminescent devices constructed according to this invention may be employed as a self-contained cathodoluminesccnt cell. Alternatively. the cells may be arrayed in a display panel having one output level. that is. a panel which is not capable of yielding a gray scale. but rather is either fully on or fully off. An example of a commercially useful panel having one on level would be an alpha numeric display panel. or the like. wherein alphanumeric characters are displayed at one intensity level.

It is contemplated however that the invention may be more usefully employed in applications wherein it is desired to have multiple light level rendition. that is. wherein it is possible to display a gray scale". An example of an application contemplated in which a gray scale capability is necessary is a black and white or color television display panel. A television display panel may comprise an array or matrix of cathodoluminescent cells according to this invention. each of which is capable of yielding a luminous output at any of a selected number of discrete output levels. or in a continuum of light output levels. To this end. it is desirable that control means be provided which is responsive to an applied control voltage for modulating the flow of electrons from the electron-multiplier 38 to the phosphor screen 58 and thus the amplitude of the light emitted by the screen. In the illustrated FIG. 3 embodiment. control electrode means are shown schematically as taking the form of a control grid 63 flanked by apertured electrodes 64, 65. The electrodes 64, 65 serve to isolate the control grid 63 from fields in the electron multiplier 38 and in the electron accelerating region of the device. The electrodes 64, 65 may have applied thereto a common voltage which is somewhat greater than the voltage applied to the last dynode 52. As will become evident hereinafter. electrodes 64. 65 may comprise windowed. electrically conductive plates.

It is also deemed to be desirable to provide bafflc means between the electron-multiplier 38 and the ac celerating anode 60 for blocking high energy electrons which might be emitted by the electron-multiplier 38 and for blocking passage to the cathode 40 of ions which might be generated in the region between the baffle means and the accelerating anode 60. In the FIG. 3 representation. baffle means are illustrated in highly schematic form as taking the form of a secondaryelectron-emissive plate 66 having a surface angled with respect to the axis of the electron-multiplier 38 for blocking high speed electrons and an ion-blocking plate 68 for blocking the passage to the cathode 40 of ions generated in the electron accelerating region. The function of the plates 66. 68 will become more apparent as other. more structural. embodiments are described hereinafter.

FIG. I4 illustrates, in more structural form than FIG. 3, cathodo-luminesccnt devices according to this invcntion incorporated in a display panel 69. The panel 69 is illustrated as being bounded by a rear wall 70 and a faceplate 71. In the panel 7I. the cathodes are shown horizontal cathode strips 72. Five dynodes, constituting part of an electron-multiplier 74, are depicted at 76, 78, 80, 82 and 84. Voltages of ever-increasing potcntial are supplied to the dynodes 7684 from a volt age divider 86.

Beam control means are illustrated as comprising a pair of electrically conductive grid-isolating electrodes 88, 90. Windows 89 are provided for passing the electron beams. Sandwiched between the electrodes 88, 90 is a control grid 91. The control grid 91 may take the form of a dielectric support plate 92 containing conductively metalized apertured grid strips 93. The discrete grid strips 93 are individually controlled by signals developed in signal processing and scan control circuitry. represented schematically at 94.

The FIG. 4 embodiment includes baffle means for blocking the passage of high energy electrons from the electron-multiplier 74 into the accelerating region of the device and for preventing feedback of high energy ions to the cathode from the electron accelerating region of the device. The accelerating region is the region between the beam control means and the accelerating electrode, preferably located on the back of the faceplate 7I. In the illustrated FIG. 4 embodiment, the firstdescribed baffling function is accomplished by a secondary-electron-emissive baffle plate 95. The latter baffling function is performed by electron-opaque areas 96 on the grid-isolating plate 90.

As noted above, it is contemplated that cathodoluminescent devices constructed according to this invention may be incorporated in an image display panel such as a television reproducer. FIG. is a highly schematic perspective view of a television display panel 1 l2 constituting a part of a television receiver. The panel I12 incorporates an X-Y matrix of cathodo luminescent devices according to this invention. The display panel 112 is illustrated as comprising a rear panel wall 4 on which is disposed an array of horizontally oriented line or strip cathodes 116. At the forward end of the panel 112 there is provided a transparent faceplate 118 on the back surface of which is disposed an array of sequentially repetitive, vertically oriented red-emissive, blue-cmissive and green-emissive phosphor strips (not shown).

In FIG. 5 there is illustrated a series of column leads 120 which lead from column current control circuitry I22 to control means such as the grid strips 93 in the FIG. 4 embodiment. Row selection and drive circuitry. shown schematically at I24, along with the column control circuitry 122, provide a modulated raster scan of the panel 112. The row selection and drive circuitry 124 and the column circuitry 122 may be constructed following principles well known to those skilled in the art.

In operation, the uppermost horizontally extending line of the cathode-luminescent devices is activated by application of appropriate potentials on the uppermost cathode 116. A line of video information which has, for example, been received by an antenna 126, been processed appropriately in a processor I28 and been stored in a line storage memory 130, is applied in parallel to a full row or a portion of a full row of cathodoluminescent devices. The video information is applied, as described, to control grids within the cathodoluminescent devices. The line of video information is maintained for a horizontal line display period. In an allotted retrace time. typically 10 microseconds of the 63 microsecond line time. the first video line is deactivated and the next successive line or the line after that (depending upon the means for effecting vertical raster interlace) is energized. A second line of video information which has been stored in the memory I30 is applied to the second video line. A complete vertical scan of the panel to display a full video image is accomplished in this manner.

If satisfactory luminous intensity is developed in the cathodo-luminescent devices, the line of stored information can be displayed during the retrace interval. This mode of operation would require one, rather than two, video storage memories. If insufficient intensity is obtained, the video information must be sim ultaneously written into one set of storage elements while another memory controls the display. Vertical commutation may be accomplished using discrete or multiphase scanning signals.

FIGS. 6-8 illustrate a color television display panel representing a preferred embodiment of the principles of this invention. The FIGS. 6-8 embodiment is illus trated as comprising a faceplate 134 on the rear surface of which is disposed a vertically oriented. periodically repetitive sequence of red-emissive, blue-emissive and green-emissive phosphor strips 136. An accelerating anode 138 comprising a layer of electrically conductive material (aluminum. for example) is deposited over the phosphor strips 136 and is adapted to receive a relatively high applied voltage for accelerating the electron beams 139 (to be described) to high energies for impingement on the phosphor strips 136.

The FIGS. 6-8 panel includes a rear enclosure plate 140 which may be composed of glass or other suitable material, on which is deposited a series of horizontally arranged cathode strips 141. The cathode strips 141 function as cold cathodes and may be composed of a material such as aluminum or other suitable materials, certain of which are suggested above. Each cathode strip 141 forms part of an electron-multiplier which includes a plurality of discrete, serially arranged, secondaryelectron-emissive dynodes 142, 144, 146, I48, I50, I52, I54 and 155 for multiplying electrons emitted from the cathode strips 141.

In the illustrated preferred FIGS. 6-8 embodiment, the dynodes 142-155 are illustrated as being formed from a series of spaced pairs of dynode sheets 156, 158. The dynode sheets 156, 158 each comprise a sheet of electrically conductive material, preferably berylliumcopper, in which is integrally formed from the sheet material a matrix of flaps 160. The flaps 160 may be formed by photo-etching away the flap boundaries and then stamping or pressing out the flaps. The dynode sheets 156, 158 are preferably formed similar to each other except that the dynode flaps are deflected in opposite directions.

A dynode structure in the form of sheets with flaps bent out to form the seeondary-electron-emissive elements and certain other structural and fabrication principles embodied and revealed in the FIGS. 6-8 embodiment do not, per se, constitute a part of this invention but are described and claimed in the referent copending application Ser. No. 538,486, filed Jan. 3, I975, assigned to the assignee of the present invention.

Whereas each of the flaps 160 may be formed to act as a dynode element for a single horizontal image line element, as shown, it is preferable the flaps be wider so as to embrace a number of image line elements six for example. By this approach, fabrication of the flaps is vastly simplified, yet interstices are created between flaps for increasing the mechanical integrity of the panel structure.

The pairs of dynode sheets 156, 158 receive applied voltages ever-increasing in positive polarity in a direction away from the cathode strips 141, which pattern of voltages may be developed by the use of voltage divider means as shown at 86 in FIG. 4. As shown by the electron paths in FIG. 7, the first dynode 142 is not actually an electron-multiplying element, but rather serves as a field-forming electrode which deflects the electrons emitted by the cathode strips to the second dynode 144. The pairs of dynode sheets 156, 158 are held in electrical union but are spaced each from each adjacent pair of sheets by means of spacers 162 which may, for example, be composed of glass or other suitable insulating material. The spacers 162 may be fabricated as the vertically spaced bridges between panelwide slit windows (aligned with the windows in sheets 156, 158) etched in a glass plate. The spacers are shielded from the electron beams by the dynodes 142, 155 such that fields due to surface charges on the insulators do not substantially alter the charged particle trajectories. The spacers 162 serve a number of functions. They control the spacing of the dynode sheets 156, 158 from neighboring dynode sheets. Secondly, they provide periodic front-to-back support across the expanse of the panel. Thirdly, the spacers 162 prevent buckling or bending of the sheets to prevent electrical short circuiting between adjacent sheet pairs.

A field-fomiing output electrode 164, including flaps 165, 166, is spaced beyond the last dynode sheet 158a and serves to form an electric field which guides the electron beam through the window formed between the flaps 165, 166 and into an electron control section or region of the panel. described below. The FIGS. 6-8 electron-multiplier is illustrated as having the capability ofa gain of approximately I000. Suitable potentials which may be applied to the dynodes 142-155 and other electrodes in the panel are shown in FIG. 7. By fabricating the electron-multiplier dynodes for the entire panel as flaps bent from electrically conductive sheets stacked to form a multiple dynode electronmultiplier, very substantial economies in panel fabrication are effected.

As in the above-described embodiments, the electron-multiplier serves to establish a source of electrons for acceleration to high energies for bombarding the phosphor strips 136. Control means for controlling the flow of electrons from the electron-multiplier to the phosphor strips 136 is illustrated in the preferred FIGS. 6-8 embodiment as taking the form of a stack of vertically oriented electrodes 168, 170, 171, 172, 174, 175 and 176. The electrodes 168-176 are divided into three functional groups by vertically oriented, horizontally spaced insulators 178, 180, which may, for example, comprise windowed glass plates. The first group of electrodes, comprising electrode 168, and the third group, comprising electrodes 174, 175 and 176, receive potentials effective to isolate the central group of control electrodes 170, 171, 172 from stray fields. See the exemplary potentials illustrated in FIG. 7. The control electrodes receive a bias voltage on which is superimposed a modulating signal voltage which may, as shown in FIG. 7, for the illustrated embodiment, take the form of a I900 volt bias modulated by a signal having a maximum peak-to-peak swing of 40 volts. The control electrodes -172 are insulated from horizontally adjacent control electrodes by insulators 181.

The electrodes 168, 174, 175 and 176 may be formed as physically and electrically united conductive plates (metalized glass plates or sheets of conductive materi als, e.g.) having windows for passing the electron beams. One of such windows is shown in electrons 168 as 184. These electrodes preferably extend horizontally and vertically across the entire panel.

The insulators 178, 180 are also preferably formed as plates having beam-passing windows, except, of course, the insulators are formed of an electrically noneonductive material such as glass. In outward appearance, the electrodes 168, 174, 175 and 176 and the insulators 178, 180 closely resemble the grid-isolating plates 188 and 190 constituting part of the FIG. 4 embodiment.

The beam control electrodes 170-172 must be individually controllable, column-by-column, since signal information to be imparted on the individual electron beams reaching the phosphor strips 136 is carried on these electrodes. The three electrodes 170-172 are preferably electrically conductive strips which are physically and electrically united to act as a single control element. The electrodes 170-172 also have win dows for passing the electron beams. The electrodes 170-172 thus have the same function as the grid strips 93 in the FIG. 4 embodiment and a similar construction, except for having three united electrodes operating as a single electrode, rather than a single electrode.

In order to insure that each of the triads of tied electrodes 170-172 are each isolated from their horizontally spaced neighbors, vertically oriented insulators 181 are provided (see FIG. 8). The insulators I81 preferably extend continuously from the top to the bottom of the panel and may be composed of glass or other suitable insulating material. I

The beam-passing windows in the electrodes 168, 170-172, 174-176 and insulators I78, 180 are successively vertically offset such that they aggregatively define angled beam-conducting channels through the beam control means. The opaque portions 186 of the electrode 184 act as a baffle which precludes entry into the beam accelerating region of high speed electrons generated in the electron-multiplier. Areas such as shown at 182 on the field-forming electrode I64 act to block the rearward passage of positive ions which might he generated in the beam acceleration region. Such baffling may not be necessary in all applications.

The electrodes are spaced from the faceplate 62 by horizontally oriented. electrically insulative (glass. for example) spacers 198. The spacers I98 are preferably disposed between every other line (i.e., between each lace-interlacc pair). Alternatively, other vertical separation distanccs may be employed. depending on the size of the panel and other electrical or structural considerations. In a small panel. simplified support structures may be employed.

Alternatively. vertically oriented. horizontally separated spaccrs may be used to provide the necessary structural rigidity for the panel. These would preferably be disposed in the location of and in substitution for every other bluc-emissive phosphor strip. Since the resolving ability of the human eye to blue-wavclcngth light images is relatively poor, the elimination of alternate blue-emissive phosphor strips will have a negligible effect on the perceived overall picture quality. These spacers 198 serve also to periodically support the faceplate. preventing bending or breakage due to atmospheric forces.

In order to precisely control the acceleration field in the acceleration region, it may be necessary to provide a series of electrically conductive ribbons, as shown at 202, on the sidewalls of the spacers 198. The ribbons 202 are adapted to receive a progression of voltages effective to achieve a satisfactory beam acceleration characteristic and to preclude interference with the beam by stray charge-generated fields or the like. An example of a voltage pattern suitable for application to the ribbons 202 is shown in FIG. 7.

In accordance with an aspect of this invention, beam deflecting means may be provided for controlling the vertical position of the electron beams in the panel, for example to effect interlace of successive display fields. In the illustrated embodiment. to deflect the electron beams for intcrlace purposes, a deflection voltage. generated, e.g.. by deflection signal generator 203, may be applied to the first ribbons 2021:, 202/). Sec FIG. 6. By application of an appropriate negative deflection voltage to ribbons 2021: (a few hundred volts, for example) and a complementary positive deflection voltage to ribbons 20217, the electron beams may be deflected downward during raster interlace. The interlace deflection signals must, of course, by synchronized with panel scan signals and synchronization signals.

FIG. 8 is a view of the control and acccelerating regions of the device taken along section lines 88 in FIG. 6. Electric fields which are established in the control and accelerating regions cause the electron beams to be converged or pinched horizontally such that the ultimate beam cross-sectional configuration upon impingcmcnt with the phosphor strips I36 is horizontally narrowed.

FIG. 8 illustrates a triad of luminescent devices or cells 204, 206, 208, taken by way of example to be associated. respectively, with a red signal picture element, a blue signal picture element and a green signal picture element. In the illustrated FIG. 8 embodiment. by way of example, the control electrodes I70, 171, 172 controlling the red-associated cell 204 carry a signal voltage of minus 30 volts which is effective to completely shut off the red-associated electron beam and thus prevent the luminescence of the red-emissive phosphor strip 136R. The control signal associated with blue information is applied to the electrodes I70, 171. I72 controlling the blue-associated cell 206 and. in the illustrated embodiment, is shown as being of such a value (minus 25 volts, e.g.) as to admit passage of a relatively low intensity electron beam 1393 to the blueemissive phosphor strip I368. The green information is shown as being a signal of greater value positive than that applied to either the redassociated or blueassociated cells 204, 206 (minus 20 volts, e.g. permitting a relatively intense green-associated electron beam 1390 to impinge upon the green-emissive phosphor strip 136G. Thus the integrated luminous output of the triad of cells would be perceived as a predominantly green image somewhat desaturated by blue light.

The invention is not limited to the particular details of construction of the embodiments depicted and other modifications and applications are contemplated. For example. rather than using control electrodes in the accclcration region, such as electrodes 170-172 in FIGS. 6-8 to modulate the flow of electrons to the phosphor strips 136, control structures of other types in the same or different regions of the device may be employed to control the flow of electrons from the electronmultiplier or to control the output of the electronmultiplier itself. Rather than operating the electronmultiplier in a mode wherein it is either off or driven to saturation, the electron-multiplier may be activated in a non-saturated state at a predetermined intermediate level of output. If operated in a maximum output mode. it may be possible to avoid storing all or part of a line interval of information and display only in the retrace interval. Rather than switching the electronmultiplier by application of a switching voltage to the cathode, a switching voltage may be applied to other suitable electrodes within the device such as one of the dynodes. It is contemplated that the output beam may be deflected on the phosphor screen, as by means of suitably structured and excited deflection electrodes, for purposes other than interlace scanning. Certain other changes may be made in the above-described apparatus without departing from the true spirit and scope of the invention herein involved and it is intended that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.

I claim:

I. A cathode-luminescent device comprising:

wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;

an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential different there-across, said electron-n'iultiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, said electronmultiplier being constructed to provide a clear path for ions such that some of said ions feed back to said cathode to cause said cathode to emit elce trons;

phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons;

accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electronmultiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; and

activating means for selectively causing the feedback loop gain of said electro-multiplier to be at least unity to drive said electronmultiplier to an on state associated with a predetermined high level of avail able electronmultiplier current and for selectively causing the feedback loop gain of said electron multiplier to be less than unity to drive said electronmultiplier to an off state associated with negligible electron-multiplier current 2. The device defined by claim 1 wherein said electron-multiplier comprises a plurality of discrete. serially arranged, secondary-electron-emissivc dynodes disposed between said cathode means and said electron-multiplier anode means and adapted to receive applied voltages ever-increasing in positive polarity in a direction away from said cathode, but substantially less than the voltage applied to said accelerating anode means, said electron-multiplier including an iongeneration region in which said positive gas ions are generated, said dynodes being arranged so as to permit some of said positive gas ions generated in said electron-multiplier to be accelerated to said cathode means to cause said cathode means to emit additional free electrons.

3. The device defined by claim 1 including control means responsive to an applied control voltage for modulating the fiow of electrons to said phosphor means and thus the amplitude of the light emitted by said phosphor means.

4. The device defined by claim I wherein said device includes baffle means disposed between said electronmultiplier and said accelerating anode means for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode means of ions which might be generated in the region between said baffle means and said accelerating anode means.

5. A cathodo-luminescent device comprising:

wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;

an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons. said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete. serially arranged. secondaryelectron-emissivc dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas. said dynodcs being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop;

phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when hom barded by high energy electrons: accelerating anode means disposed at said phosphor means and adapted to receive a predetermined ac' cclcrating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplicr when said electron-multiplier is on and for accelcrating them to high energies for impingement on said phosphor means. the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;

activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electronmultiplier on by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level; and

control means including a control electrode located within said enclosure between said electronmultiplier and said accelerating anode said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means 6. The device defined by claim 5 wherein said device includes baffle means disposed between said electronmultiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.

7. Television display panel for reproducing an image carried by an input video signal. comprising:

an array of cathodo-luminescent elements discretely excitable by row-column selective addressing. each element comprising:

wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure,

an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages everincreasing in a positive polarity in a direction away from said cathode, said electroirmultiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop,

phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons,

accelerating anode means adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electronmultiplier anode for drawing electrons from said electron-multplicr when said electron-multiplier is on and for acccelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device,

activating means for scctively causing the loop gain of said electron'multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron'multiplier on by causing said loop gain to be unity or greater wherein said electronmultiplier saturates at a predetermined saturation current level. and

control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means; and

means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.

8. The device defined by claim 7 wherein said panel includes bafflc means disposed between said electronmultiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.

9. A luminescent panel for displaying alpha-numeric characters or other light representations carried by an input signal, comprising:

an array of discretely excitable cathode-luminescent elements. each element comprising:

wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure,

an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons. said elcctronmultiplier in cluding cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electronmultiplicr generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons,

phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons,

accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accclerating voltage substantially more positive than the voltage applied to said electronmultiplier anode means for drawing electrons from said electron-multiplier when said electronmultiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, and

activating means for driving said electronmultiplier between an on state associated with a predetermined maximum available electronmultiplier current and an off state associated with negligible electron-multiplier current; and

means responsive to the input signal and coupled to said electron-multiplier of each of said elements for applying the input signal to said array of elements to cause the input signal to be reproduced on the panel as a light representation spatially varying in amplitude,

10. A cathodo-luminescent device comprising: wall means defining an enclosure containing an ionizablc gas at a predetermined low pressure;

an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electrode-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, said electronmultiplicr being constructed to provide a clear path for ions such that some of said ions feed back to said cathode to cause said cathode to emit electrons;

phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bom barded by high energy electrons;

accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron multiplier means for drawing electrons for said electronmultiplier when said electron-multiplier is on and for accelerating them to high energies for impinge ment on said phosphor means, the said predeter mined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;

activating means for selectively causing the feedback loop gain of said electron-multiplier to be at least unity to drive said electron-multiplier to an on state associated with a predetermined high level of available electron-multiplier current and for selectively causing the feedback loop gain of said clectrow multiplier to be less than unity to drive said elec tron-multiplier to an off state associated with negligible electron-multiplier current; and beam deflecting means responsive to an applied deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means. ll. Television display panel for reproducing an image carried by an input video signal, comprising:

an array of cathodo-luminescent elements discretely excitable by row-column selective addressing. each element comprising: wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete serially ar ranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages everincreasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electronanultiplier l'or emitting light when bombarded by high energy electrons acceierating anode means adapted to receive a pre determined accelerating voltage substantially higher than the voltage applied to said electron multiplier anode for drawing electrons from said electronmultiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means. the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron multiplier to assume an inactive state or for turning said electron-multiplier on by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level.

control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means. and

beam deflecting means responsive to an applied interlace deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means to effect interlace of successively displayed fields; and

means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude. 

1. A cathodo-luminescent device comprising: wall means defining an enclosure containing an ionizable gas at a predetermined low pressure; an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electronmultiplier anode means adapted to receive an applied potential different thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, said electron-multiplier being constructed to provide a clear path for ions such that some of said ions feed back to said cathode to cause said cathode to emit electrons; phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons; accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; and activating means for selectively causing the feedback loop gain of said electro-multiplier to be at leAst unity to drive said electron-multiplier to an on state associated with a predetermined high level of available electron-multiplier current and for selectively causing the feedback loop gain of said electron-multiplier to be less than unity to drive said electron-multiplier to an off state associated with negligible electron-multiplier current.
 2. The device defined by claim 1 wherein said electron-multiplier comprises a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode means and said electron-multiplier anode means and adapted to receive applied voltages ever-increasing in positive polarity in a direction away from said cathode, but substantially less than the voltage applied to said accelerating anode means, said electron-multiplier including an ion-generation region in which said positive gas ions are generated, said dynodes being arranged so as to permit some of said positive gas ions generated in said electron-multiplier to be accelerated to said cathode means to cause said cathode means to emit additional free electrons.
 3. The device defined by claim 1 including control means responsive to an applied control voltage for modulating the flow of electrons to said phosphor means and thus the amplitude of the light emitted by said phosphor means.
 4. The device defined by claim 1 wherein said device includes baffle means disposed between said electron-multiplier and said accelerating anode means for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode means of ions which might be generated in the region between said baffle means and said accelerating anode means.
 5. A cathodo-luminescent device comprising: wall means defining an enclosure containing an ionizable gas at a predetermined low pressure; an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop; phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons; accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier on by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level; and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied contrOl voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means.
 6. The device defined by claim 5 wherein said device includes baffle means disposed between said electron-multiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.
 7. Television display panel for reproducing an image carried by an input video signal, comprising: an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising: wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multplier when said electron-multiplier is on and for acccelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for sectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier ''''on'''' by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.
 8. The device defined by claim 7 wherein said panel includes baffle means disposed between said electron-multiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.
 9. A luminescent panel for Displaying alpha-numeric characters or other light representations carried by an input signal, comprising: an array of discretely excitable cathodo-luminescent elements, each element comprising: wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier anode means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, and activating means for driving said electron-multiplier between an on state associated with a predetermined maximum available electron-multiplier current and an off state associated with negligible electron-multiplier current; and means responsive to the input signal and coupled to said electron-multiplier of each of said elements for applying the input signal to said array of elements to cause the input signal to be reproduced on the panel as a light representation spatially varying in amplitude.
 10. A cathodo-luminescent device comprising: wall means defining an enclosure containing an ionizable gas at a predetermined low pressure; an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electrode-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, said electron-multiplier being constructed to provide a clear path for ions such that some of said ions feed back to said cathode to cause said cathode to emit electrons; phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons; accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons for said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; activating means for selectively causing the feedback loop gain of said electron-multiplier to be at least unity to drive said electron-multiplier to an on state associated with a predetermined high level of available electron-multiplier current and for selectively causing the feedback loop gain of said electron-multiplier to be less than unity to drive said electron-multiplier to an off state associated with negligible electron-multiplier current; and beam deflecting means responsive to an applied deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means.
 11. Television display panel for reproducing an image carried by an input video signal, comprising: an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising: wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier on by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means, and beam deflecting means responsive to an applied interlace deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means to effect interlace of successively displayed fields; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude. 